Chemical reactions in liquids: Molecular dynamics simulation for sulfur

Abstract

A combination of two-atom and three-atom interactions has been selected to represent the structural chemistry of sulfur. This model potential exhibits divalency (bond saturation) and leads to the known preference for Sn molecules to form puckered ring structures. Using this representation of the interactions, molecular dynamics calculations have been performed for 1000 sulfur atoms at the experimental liquid density. Short-range order has been calculated for the low-temperature liquid consisting of S8 cyclic molecules, and agrees qualitatively with the (imprecise) available measurements. At elevated temperatures the cyclic S8 molecules in the simulation begin to break open, and their subsequent chemical reactions yield primarily linear polymeric species. A metastable reaction intermediate in the polymerization process has been identified, a ‘‘tadpole’’ consisting of a diradical chain attached weakly to an S8 ring.